Physics of Metals and Metallography (v.116, #8)
Plasmon polaritons at the boundary between a dielectric and a nanocomposite with metallic inclusions by D. A. Evseev; D. I. Sementsov (745-752).
Properties of surface plasmon polaritons at the interface formed in a dielectric matrix by a region without inclusions and by a region with metallic nanoinclusions have been investigated. The region with inclusions is a nanocomposite in which the dielectric constant has resonance behavior caused by the plasmon resonance of metallic nanoinclusions. The frequency dependences of the propagation constant and the transverse components of the wave vector, depth of penetration, mean free path, group velocity, and longitudinal energy flux have been obtained based on the solution to the boundary-value problem and numerical analysis. A substantial influence of the dielectric constant of the matrix of the structure on the wave characteristics of surface polaritons has been shown.
Keywords: surface waves; nanocomposite; metallic inclusions
Micromagnetic structure of soft magnetic nanocrystalline Fe-based films by E. V. Harin; E. N. Sheftel (753-759).
Results of a quantitative determination of parameters of the micromagnetic structure of nanocrystalline Fe, Fe95Zr5, Fe90N10, and Fe85Zr5N10 films prepared by magnetron sputtering have been reported. The magnetocrystalline (K 1), magnetoelastic (K ME), magnetostatic (K MS), and surface (K a,s) anisotropy constants have been shown to be components of the effective local anisotropy (K eff) constant determined experimentally. The shape of hysteresis loops is determined by the existence of two main components of macroscopic effective magnetic anisotropy, one of which is caused by local (within a nanograin) magnetic anisotropy averaged over the exchange interaction length, while the other is related to magnetoelastic anisotropy due to residual macrostresses.
Keywords: nanocrystalline; soft magnetic FeZrN films; magnetic anisotropy; magnetic structure
Structural-phase composition, structure of the surface, magnetostatic and microwave properties of powders produced by milling of Fe in polystyrene with additions of surfactants by S. F. Lomaeva; A. N. Maratkanova; A. V. Syugaev; K. N. Rozanov; D. A. Petrov (760-767).
The effect of additions of surfactants (stearic and perfluorononanoic acids, stearylamine, and of their mixtures) on the morphology, structural-phase composition, structure of the surface, and magnetostatic and microwave properties of ferromagnetic powders obtained by the joint high-energy milling of Fe and polystyrene has been investigated. It has been shown that the use of a mixture of stearic and perfluorononanoic acids during milling made it possible to obtain particles of plate-like shape with minimum changes in the phase composition and to produce shells on their surface that consist of the surfactant molecules. All of these factors have positively affected the microwave properties of the composites prepared from thus obtained powders.
Keywords: powder of carbonyl iron; polystyrene; high-energy milling; surfactants; microwave properties
Magnetocrystalline anisotropy of Er2(Fe1 − x V x )17 compounds by P. B. Terentev; N. V. Mushnikov; E. G. Gerasimov; V. S. Gaviko; L. A. Stashkova (768-773).
The magnetic properties and magnetic anisotropy of the Er2(Fe1−x V x )17 compounds (with x = 0–0.05) have been studied. The Curie temperature (T C) of the compounds has been found to increase as the vanadium concentration increases. It has been shown that the Er2(Fe1 − x V x )17 compounds have the easy-plane anisotropy in the temperature range from, 77 K to T C. Magnetization curves have been measured and the temperature dependences of the K 1 and K 2 anisotropy constants have been calculated. Contributions from the Er and Fe magnetic sublattices to the magnetic anisotropy constants were distinguished. An analysis of the obtained data allowed us to conclude that the cause for the existence of first-order magnetization processes in Er2Fe17 at low temperatures is a positive contribution from the Er sublattice to K 1 and a negative contribution from it to K 2.
Keywords: magnetic phase transitions; magnetic anisotropy; rare-earth intermetallic compounds
Determination of the magnetic losses in laminated cores under pulse width modulation voltage supply by N. Vidal; K. Gandarias; G. Almandoz; J. Poza (774-780).
In the laminated ferromagnetic cores employed in transformers and electrical machines energy losses occur resulting in a warming effect and efficiency decrease. Normally, manufacturers only provide iron losses data when a sinusoidal voltage supply is applied, but the actual operating characteristics of electrical machines include non-sinusoidal supplies, in particular pulse-width modulation (PWM). This information can be experimentally obtained, but only measuring systems that have function generators with arbitrarily programmable waveforms allow measurements in the presence of higher harmonics. Therefore, having an analytical tool to obtain the most accurate estimation of the magnetic losses is of great interest in addressing the design of electric machines. This paper validates an analytical-expression-based procedure, which delivers results with acceptable accuracy under all operating conditions for the estimation of losses in laminated cores. In addition, it investigates the influence of the modulation amplitude and the switching frequency of the PWM signals in the magnetic losses of soft magnetic materials. For this purpose, non-oriented fully processed electrical steel strips have been measured in a commercial AC permeameter using a single strip tester.
Characterization of nanocomposite a-C:H/Ag thin films synthesized by a hybrid deposition process by M. Venkatesh; S. Taktak; E. I. Meletis (781-790).
Silver containing amorphous carbon films were deposited on Si wafer using a hybrid deposition process combining d.c. magnetron sputtering and PECVD. The concentration of Ag in the films was varied from 1.3 to 8.3 at % by changing d.c. magnetron current of Ag target. The influence of incorporated Ag in the a-C:H on the atomic bond structure of the films were investigated by XPS, FTIR, Raman, and HRTEM methods of analysis. The XPS, FTIR, and Raman studies demonstrated that as the silver concentration increased in the a-C:H, sp2 bonding content increased and a-C:H films changed to more graphitic structure. The high resolution TEM cross sectional studies revealed that crystalline Ag particles formed with a size in the range of 2–4 nm throughout an amorphous a-C:H matrix.
Keywords: Ag/DLC films; Raman analysis; atomic bond structure; nanocomposite; XPS; hybrid deposition
Studying mechanosynthesized Hägg carbide (χ-Fe5C2) by V. A. Barinov; A. V. Protasov; V. T. Surikov (791-801).
Methods of thermomagnetic analysis and Mössbauer experiments (57Fe) were used to investigate the formation of Hägg carbide (χ-Fe5C2) under the conditions of mechanical milling of α-Fe in a medium of liquid hydrocarbons. It has been established that, with the employed parameters of milling, the synthesis of χ carbide begins after the completion of the stage of the formation of cementite (θ phase). The borderline of temperature stability of the monophase state of the χ carbide has been determined to be no more than 800 K. At T > 800 K, χ carbide decomposes into cementite and free carbon. The optimum temperature of heating of the synthesized Hägg carbide at which the population of the crystallographically nonequivalent positions of the Fe atoms is close to the ideal (0.2: 0.4: 0.4) is 775 K; the Curie temperature is T C = 520 K. The analysis of the Mössbauer data and of the results of a geometrical simulation of the configurations of Fe atoms in the the χ carbide unit cell made it possible to establish that the above relationship between the populations of positions is satisfied with the allowance for the anisotropic component h an of the field of hyperfine interaction. Under the effect of h an, the crystallographically equivalent atoms Fe(4e) become nonequivalent (Fe(e 1) and Fe(e 2)) in the magnetic sense. This specific feature manifests in the appearance in the presence of the distribution of hyperfine fields P(H) of two Mössbauer contributions, i.e., p(e 1) and p(e 2) with equal fractions of iron atoms in each of the contributions f Fe(e 1) = = f Fe(e 2) = 0.1 with the magnitudes of the fields H ≈ 11 and 16 T, respectively.
Keywords: mechanosynthesis; Hägg carbide (χ-Fe5C2 carbide); magnetic susceptibility; Curie temperature T C ; parameters of hyperfine interactions
Stages of austenitization of cold-worked low-carbon steel in intercritical temperature range by D. O. Panov; Y. N. Simonov; L. V. Spivak; A. I. Smirnov (802-809).
Austenization processes in 10Kh3G3MF low-carbon steel in the initially cold-worked state are investigated during its continuous heating in an intercritical temperature range. The austenization of this steel has three stages, which is shown by dilatometry, differential scanning calorimetry, and transmission electron microscopy. The thermokinetic diagram of the austenite formation in 10Kh3G3MF steel is constructed. Critical points A c1 and A c2 and temperature ranges of austenite formation at every stage of the α → γ transformation at heating rates of 0.6–400 K/s are determined.
Keywords: intercritical temperature range; austenization; low-carbon steel; dilatometry
On the effect of nonequilibrium vacancies on the melting and pore formation in ultrafine-grained aluminum alloys subjected to pulsed laser irradiation by P. Yu. Kikin; V. N. Perevezentsev; E. E. Rusin (810-816).
An analysis has been carried out of the experimental data concerning the interaction of pulsed laser radiation with the ultrafine-grained (UFG) Al-Mg alloys obtained by the methods of severe plastic deformation. It has been shown that the melting and pore formation in the UFG alloys under the effect of laser radiation start earlier than in their coarse-grained analogs. The observed behavior of the alloys can be explained from the united positions based on the concepts of the influence of the high concentration of nonequilibrium vacancies on the ability of the alloys to absorb the laser radiation and on the process of pore formation.
Keywords: laser radiation; ultrafine-grained aluminum alloys; nonequilibrium vacancies; melting; pore formation
Structure and properties of joints produced by ultrasound-assisted explosive welding by A. P. Peev; S. V. Kuz’min; V. I. Lysak; E. V. Kuz’min; A. N. Dorodnikov (817-822).
This paper presents the results of the effect of ultrasound on explosion welded materials. It has been established that simultaneous treatment with ultrasonic vibrations and explosion welding of the materials to be welded has a significant effect on the structure and properties of the heat-affected zone of formed joints.
Keywords: explosive welding; ultrasonic vibrations; structure; microhardness; strength
Friction-induced structural transformations of the carbide phase in Hadfield steel by L. G. Korshunov; V. V. Sagaradze; N. L. Chernenko; V. A. Shabashov (823-828).
Structural transformations of the carbide phase in Hadfield steel (110G13) that occur upon plastic deformation by dry sliding friction have been studied by methods of optical metallography, X-ray diffraction, and transmission electron microscopy. Deformation is shown to lead to the refinement of the particles of the carbide phase (Fe, Mn)3C to a nanosized level. The effect of the deformation-induced dissolution of (Fe, Mn)3C carbides in austenite of 110G13 (Hadfield) steel has been revealed, which manifests in the appearance of new lines belonging to austenite with an unusually large lattice parameter (a = 0.3660–0.3680 nm) in the X-ray diffraction patterns of steel tempered to obtain a fine-lamellar carbide phase after deformation. This austenite is the result of the deformation-induced dissolution of disperse (Fe, Mn)3C particles, which leads to the local enrichment of austenite with carbon and manganese. The tempering that leads to the formation of carbide particles in 110G13 steel exerts a negative influence on the strain hardening of the steel, despite the increase in the hardness of steel upon tempering and the development of the processes of the deformation-induced dissolution of the carbide phase, which leads to the strengthening of the γ solid solution.
Keywords: Hadfield steel; friction action; dispersion and dissolution of carbide phase
Structural changes in Bi-43 wt % Sn eutectic alloy under superplastic deformation by V. F. Korshak; Yu. A. Shapovalov; O. Prymak; A. P. Kryshtal; R. L. Vasilenko (829-837).
Methods of scanning electron microscopy have been used to study the microstructure of superplastically deformed samples of eutectic alloy Bi-43 wt % Sn. The observed specific features of the deformation relief of the samples reveal the active development of the viscous dislocation-diffusion flow under superplasticity conditions. The manifestation of the hydrodynamic mode of deformation has been revealed under these conditions. The opportunity of the realization of viscous mechanisms of the transport of substance and of the manifestation of the effect of superplasticity are explained by the appearance in the material of a state that is characterized by a high dislocation density and low strength properties. An additional increase in the dislocation density and softening under superplasticity conditions are attributed to the occurrence of structural and phase transformations stimulated by deformation, the relaxation of significant internal elastic stresses, and the instability of the structural state of the initially nonequilibrium alloy in the field of mechanical stresses. Factors responsible for the appearance of significant internal elastic stresses in the alloy are analyzed.
Keywords: superplastic deformation; viscous flow; hydrodynamic mode of deformation; internal elastic stresses; nonequilibrium phase state; eutectic alloy
Behavior of magnetic characteristics in promising nitrogen-containing steels upon elastoplastic deformation by E. S. Gorkunov; E. A. Putilova; S. M. Zadvorkin; A. V. Makarov; N. L. Pecherkina; G. Yu. Kalinin; S. Yu. Mushnikova; O. V. Fomina (838-849).
We report on the studied influence of the applied normal and tangential stresses, as well as their combined effect on the structure, phase composition, and magnetic properties of three high-nitrogen steels (HNS). Two of the studied steels in the initial state had an austenitic structure and were diamagnetic. The third steel, according to the data of the X-ray diffraction and metallographic analysis, contained 7% δ-ferrite in its composition, which specifies its ferromagnetic properties. The nitrogen steels studied in this work have demonstrated the stability of the phase composition, as well as of the magnetic properties at various loading conditions, and, thus, can be used in the production of articles and elements of structures that are required to exhibit low magnetization and high stable magnetic characteristics under an applied force. Parameters that can be used as the informative ones when estimating changes that occur upon the production and exploitation of articles and elements made of HNSs with small contents of δ ferrite have been determined.
Keywords: high-nitrogen corrosion-resistant steel; stability of magnetic characteristics; normal stresses; tangential stresses